Recently, with social demand for energy saving, the requirement for vehicle fuel consumption reduction is being severer. To satisfy the requirement, it has become desired to reduce the rolling resistance for tire performance. As a method for reducing tire rolling resistance, there has been investigated a method of optimizing a tire structure; however, as the most general method, there is employed a method of improving the low-heat-generation property of tires by using a low-heat-generation material as a rubber composition.
Further, from the viewpoint of enhancing the safety in vehicle driving, it is important to secure braking performance on wet roads (hereinafter this may be abbreviated as “wet braking performance”), and it is also desired to secure wet braking performance along with improving the low-heat-generation property.
On the other hand, PTL 1 proposes a tire that uses, as the tread thereof, a rubber composition containing a rubber component containing an amine-based functional group-modified styrene-butadiene copolymer and a specific silica. Further, PTL 2 discloses a rubber composition for tire treads that contains a rubber component containing three types of rubbers of an emulsion-polymerized styrene-butadiene copolymer rubber, a terminal-modified solution-polymerized styrene-butadiene rubber and a butadiene rubber, and silica.
However, a rubber composition is desired capable of more highly satisfying both low-heat-generation property and wet breaking performance.
PTL 1: WO2009/084667
PTL 2: JP-A-2010-275386